Apparatus for preparing planographic offset printing plates



June 10, 1969 R. c. GRAHAM 3,448,720

APPARATUS FOR PREPARING P'LANOGRAPHIC OFFSET PRINTING PLATES Filed July12, 1967 -91: Cfml wm INVENTOR Robert C. Grdhom BY %M, W Z a CZ, 29 6 zzuw ATTORNEYS United States Patent Office 3,448,720 Patented June 10,1969 3,448,720 APPARATUS FOR PREPARING PLANOGRAPHIC OFFSET PRINTINGPLATES Robert C. Graham, Florham Park, N.J., assiguor to WoodIndustries, Inc., a corporation of Virginia Filed July 12, 1967, Ser.No. 652,839 Int.9Cl. B05c 9/06, 9/12, 9/08 US. 'Cl. 118-10 4 ClaimsABSTRACT OF THE DISCLOSURE Background of the invention This inventionrelates to an apparatus for preparing planographic offset printingplates used in lithographic printing processes.

It has long been known in the lithographic industry that a wipe-one orpresensitized offset planographic printing plate image may be developedby what is known as a one-step hand developing process. In such aprocess the offset planographic printing plate is first covered with alight sensitive diazo resin and then exposed through a negative stencilto a strong light source such as a carbon arc. The light sensitive diazowhen subjected to such light is converted to an insoluble phenol whilethe shaded portion not illuminated remains water soluble. Theapplication of a conventional developing agent and the rubbing into thesurface of the offset planographic printing plate of such a developingagent, as for example, by a sponge, causes a removal of the unexposeddiazo and a deposition onto the insoluble diazo resin of a protectivevinyl or epoxy resin layer. The planographic plate is then ready for aprinting press.

Where this hand developing process is used to produce newspaper printingplate, the following process is usually followed. A typewritten setup ormakeup for one plate which is equivalent to one page of a newspaper isprovided in any desired manner, and includes the typed articles, anypictures, various kinds of art work, and headlines of different sizetype, all assembled on a suitable cardboard or other support. The setupis photographed and after development of the photographic negative, itis transferred to or burned into a sensitized emulsion of diazo that hasbeen spread over a grained aluminum alloy plate or other support, whichplate later becomes the printing plate with letters, line illustrations,and halftones therein. The pictures are also readily transferred withthe typed articles to the plate, and in the plates become the halftonesunder the broad term. artwork. The plate as thus prepared is thensubjected to a developing operation using chemistry of the typediscussed above. The chemistry of the developer is worked into thesensitive coating by rubbing by hand with a sponge until a visible imageappears and a residual gum arabic molecular layer replaces theunhardened or unexposed diazo.

The disadvantages of a hand operation for offset printing platedevelopment are: The process is slow and expensive; there is no'uniformity of pressure in applying the protective coating due to theattempt to cover by hand rubbing large surfaces by either a circular orback and forth motion of the sponge; defective printing often resultsfrom inadequate depositing of the protective coating on large printingareas of illustrations or of solid color; drying of the developer oncertain portions of the plate before it can be rubbed in due to thelarge and cumbersome size of the lithographic plate; and the timerequired for hand development.

A further disadvantage of the hand developing is that while hand methodsgive a coating of epoxy resin or vinyl lacquer over the printing areas,different types of images such as halftones, solids and lineillustrations require additional hand rubbing and extra pressure on thesponge to apply the full thickness of protective material, and theresults of such rubbing do not indicate the thickness of the materialapplied. A proper thickness of protective material is necessary in alithographic printing plate to withstand the various abrasive actionssubjected on the plate by the lithographic printing press blanket, inkand paper.

A still further difficulty with the hand method is in applying thedeveloping solution. -It is now the practice of the craftsman to pour anamount of developer supposedly sufficient to process the plate into thecenter of the plate and to work his sponge from that reservoir. Suchprocedure may cause and does cause contamination of the developing fluidby the removed diazo salt that is unexposed so that the process isslowed by resultant working of the contaminated developing solution overundeveloped image areas such that the remaining image may have inherentweaknesses.

Summary of the invention Briefly, I overcome the difficulties associatedwith conventional hand developing by providing for a developer apparatuswhich has therein a receiving station for receiving a printing plate, adispensing station whereby a developer solution may be dispensed evenlyover the complete surface of one side of the plate, a rubbing stationwherein a rubbing roller contacts the surface of the plate evenly overits complete width, a washing station wherein the complete plate iswashed to remove the developer solution therefrom, and a dischargestation. A propelling means is provided to propel the plate through allof the stations. The roller comprises a shaft which has thereon aplurality of annular discs which are made of a pliable absorbentmaterial and which, in turn, are separated by annular spacers, whereinthe spacers and discs are mounted concentrically on the shaft. Theroller is also provided with compression means whereby the spacers anddiscs may be compressed axially, and also with locking means whereby thespacers are prevents from relative rotation with the shaft.

An apparatus constructed as outlined above will provide a uniform andeven rubbing action of the roller with respect to the plate which willcause a uniform thickness of epoxy resin or vinyl to adhere to theprinting image. Further, the uniform pressure of the developing rolleron the printing plate causes an even and uniform deposition of theprotective element of the developer onto the protected image surface insufficient quantity and thickness to prevent abrasion by ink, paper orprinting press blanket.

By having the dispensing means extend across the complete width of theplate, a proper amount of developing solution is assured over the entiresurface of the plate with the result that the possibility ofcontamination of the solution is reduced and that a stronger film ofvinyl or epoxy resin remains after the developing cycle.

Descripti n of the drawings FIG. 1 is a diagrammatic sectional side viewof an apparatus constructed according to the invention;

FIG. 2 is a diagrammatic side view of the opposite side of the apparatusof FIG. 1;

FIG. 3 is an enlarged partial sectional view of a developer rollerconstructed according to the invention.

Description of the prefer-lied embodiment Referring to FIG. 1, there isillustrated a developer apparatus 1 which has therein a receivingstation 2 for receiving a planographic printing plate P, a dispensingstation 3 where a developing solution is dispensed onto one surface ofthe plate, a rubbing station 4 where the solution is rubbed into theplate, a washing station 5 where the developing solution is removed fromthe plate, and a discharge station 6 where the plate P is dischargedfrom the apparatus.

The receiving station 2 has shelf 7 which is attached to the side wall 8of the apparatus and on which a plate may be supported. The wall 8- hasan opening '9 in the side thereof through which a plate may be pushed soas to engage a propelling roll 10 which will pull the plate into theapparatus and propel it into the dispensing station 3.

Dispensing station 3 has therein a propelling roll 11 and a backup roll12 which pull the plate through the nip area formed therebetween andpass the plate beneath a dispensing conduit 13. Conduit 13 extends abovethe passage of the plate and over the complete width of the plate. Adeveloping solution is dispensed or sprayed onto the plate with anyexcess falling into the sump 14 from whence it is recirculated back tothe conduit .13 by the pump 15. Make-up solution may be added by meansnot shown to insure that a proper level of solution is maintained in thesump or reservoir 14.

The plate P is propelled from the dispensing station 3 by propellingroll 11 into the rubbing station 4 where it is engaged by the propellingroll 16 which pulls the plate into the nip area formed by the roll 16and rubbing roller 17. As more fully described hereafter, the rubbingroller 17 comprises in part a plurality of annular discs 18 made ofpliable, absorbent sponge-like material which rubs the upper surface ofthe plate onto which the developing solution was dispensed thus removingunexposed diazo while at the same time depositing a protective vinyl orepoxy resin layer onto the unexposed portions of the plate. A pivotablesplash guard 19 is mounted on the side walls of the apparatus ahead ofthe rubbing station 4 and is adapted to rise up and down on a plate asthe plate passes into the rubbing station and to prevent any of thedeveloping solution being dispensed by the conduit 13 from beingsplashed into the rubbing station.

The plate is propelled from the rubbing station 4 by the roll 16 topropelling roll 20* and backup roll 21 which move the plate into thewashing station 5. Spray conduits 22 and 23 extend over and below theplate and over the complete width of the plate such that both sides ofthe plate may be completely washed to remove contaminated developingsolution and any unexposed diazo remaining on the plate. The conduits 22and 23 are joined by a conduit 24 which in turn connects with a conduit25 connected to a conventional water tap, not shown. A valve 26 isincluded in conduits 25 to regulate the flow of water therethrough. Thebottom of the apparatus has a su mp 27 in which the water from thewashing station falls as well as any developing solution that does notfall into the sump 14. Sump 27 leads to a conventional drain, not shown.

Propelling roll 30 and backup roll 31 which are mounted in the washingstation and after the conduits 22 and 23 movethe plate to the dischargestation 5 through an opening 32 contained in the side wall 33 of theapparatus onto a shelf 34 mounted on the side wall 33. Shelf 34' servesas a discharge station from where the developed plate may be removed andapplied to a press. A flexible apron 35 is mounted over the opening 32and serves to contain the spray within the washing station and also toassist in wiping rinse water from the plate.

Propelling rolls 10; 11, .16, 20 and 30 are all operatively joined by adrive belt which passes over pulleys 41, 42, 43 and 44 connected on theshafts of all the propelling rolls except for roll 10. Drive belt 40' inturn is driven by a drive pulley contained within a speed reducer 46.Speed reducer 46 in turn is connected to driving motor 47 by means of adrive belt 48.

Drive motor 47 is connected by means of a drive belt 49 to rubbing roll17 by means of pulley 50 mounted on the shaft 51 of the rubbing roll.Propelling roll 10 is also driven by the belt 49. The pulley 52 ismounted on a wall of the apparatus and serves to position the belt 49.

The various pulleys connected to the rollers and the dimensions of thespeed changer 46 are so proportioned that roll 17 is rotated at a speedsuch that its peripheral speed at the area of its engagement with aprinting plate is greater than the lineal speed of the plate passingthrough the rubbing station. This results in the roll or roller engagingthe plate with a rubbing action thus assuring that unexposed diazo willbe removed from. the plate while at the same time causing a protectivelayer to be deposited onto the exposed portions of the plate. Since theroll extends the Width of the plate, the rubbing action over the widthof the plate will be uniform.

Referring to FIG. 3, it is seen that the roller 17 com prises aplurality of annular discs 18 which are positioned concentrically on theshaft 51 and which are separated by a plurality of spacers with a spacer61 and a spacer 62 being mounted on the outer ends of the roll. Thespacers themselves are locked with respect to the shaft 51 by either akey or other conventional means so that relative rotation between theshaft 51 and the spacers is prevented. The end spacer 61 abuts against astop 63 contained on the shaft 51 while the opposite end spacer 62 abutsagainst a nut 64 threaded onto the shaft 51. Thus nut 64 serves as acompression means by which the spacers and discs 18 may be compressedaxially on the shaft.

The spacers have a substantially I-shaped cross section in order tofirmly grasp the annular discs. As the spacers are moved axially by thenut 64, the I-shaped configuration digs or bites into the annular discsthus serving to lock the discs to the spacer and thus preventingrelative rotation of the discs with respect to the shaft. The spacersare provided with curved or tapered portion 65 .adjacent the shaft whichassist in assembly of the roller and particularly with the initialcontact with the annular discs.

The roll is initially assembled by first mounting the spacer 61 onto theshaft 51 such that it abuts the stop 63. A rubber disc 18 is thenpositioned onto the shaft against the spacer 61, a further space '60inserted onto the shaft, and then another disc 18 and so on until theroll is of the desired width. Finally the spacer 62 is inserted and thenut '64 is screwed on. As the nut 64 moves the parts axially against thestop 63, the tapered portion 65 will cut into the annular opening of thedisc and act to insure uniform compressibility on the internal portionof the disc such that the outer diameter of the disc will have acomparatively firm, solid surface throughout the length of the rollwhich would not necessarily be the case if a single, long cylindricalportion of a sponge material were compressed at both ends.

An advantage of the apparatus as shown is that a planographic plate ismaintained substantially fiat during processing thus reducing anytendency of bending of the plate which could result in difficulty inattaching the plate to a press. A further advantage is that as sectionsof the roll 17 become worn, they may be easily replaced simply byreplacing individual worn discs by new discs.

Having described my invention, I claim:

1. In apparatus for preparing planographic offset printing plateswherein the apparatus has a propelling means for moving a printing plateinto, through and out of the apparatus; a receiving station forreceiving a plate; a dispensing station having a dispensing means fordispensing a developing solution onto one surface of the plate; arubbing station having a rotatable roller with a pliable absorbent coveron the outer periphery thereof adapted to engage a surface of a plate torub said solution onto said plate and means for rotating the roller; awashing station having Washing means whereby opposite sides of saidplate are washed to remove the solution therefrom; and a dischargestation where .a plate is discharged from said apparatus; theimprovement which comprises having said dispensing means extend acrossthe width of a plate such that when a plate passes through saiddispensing station, developing solution will be dispensed over acomplete surface of the plate.

2. In apparatus for preparing planographic olfset printing plateswherein the apparatus has a propelling means for moving a printing plateinto, through and out of the apparatus; a receiving station forreceiving a plate; a dispensing station having a dispensing means fordispensing a developing solution onto one surface of the plate; arubbing station having a rotatable roller with a pliable absorbent coveron the outer periphery thereof adapted to engage a surface of a plate torub said solution onto said plate and means for rotating the roller; awashing station having washing means whereby opposite sides of saidplate are washed to remove the solution therefrom; and .a dischargestation where a plate is discharged from said apparatus; the improvementwhich comprises the roller having a roller shaft, a plurality of annulardiscs positioned concentrically of said shaft to form said absorbentcover where each disc is made of a pliable absorbent material, means forcompressing said discs in an axial direction with respect to said shaft,and means for locking the discs with respect to the shaft to preventrelative rotation thereto.

3. In apparatus according to claim 2 wherein said locking meanscomprises a plurality of annular spacers positioned concentrically onsaid shaft and being locked against relative rotation with respectthereto, with a spacer between adjacent discs and an outer spacer at theouter end of each outer disc at the two ends of the roller.

4. In apparatus according to claim 3 wherein said compression meanscomprises a stop on said shaft for engaging one of said outer spacersand a nut threaded onto said shaft to engage the other of said outerspacers whereby turning of the nut will cause said spacers to movetoward each other to compress said discs and to lock said discs withrespect to said shaft.

References Cited UNITED STATES PATENTS 1,281,003 10/191 s Henderson29-125 x 2,282,628 5/1942 Whann et a1 11s 109x 2,324,050 7/1943 Shelley29 -425 3,358,642 12/1967 Beck -..118--109 WALTER A. SCHEEL, PrimaryExaminer.

J. P. McINTOSH, Assistant Examiner.

US. Cl. X.R. 118-110, 314, 316

